1. Field of the Invention
The invention relates to materials and methods for decontamination of items and persons contaminated with chemical and biological agents, and more particularly to decontamination of open wounds.
2. Background Information
The capability to decontaminate (preferably neutralize, but at least remove) chemical and biological agents from human skin, or from articles handled by humans, and in particular from open-wounds of casualties is extremely valuable to the military. This capability will increase the safety and survivability of casualties and personnel in the course of medical treatment of casualties in an environment that is contaminated with chemical and/or biological threat agents, and will allow medical personnel to more readily treat casualties in a safe and effective manner.
The level of decontamination required is established by the toxicity level of the agent involved. The percutaneous values for 50% percentile lethal dose for the major Chemical Warfare Agents (CWA) are as follows:
AgentLD 50 (skin), mg/kgHD (Mustard)100GB (Sarin) 24.3GA 9.3GD (Soman) 5.0VX (Nerve Agent) 0.14 (per minute)
The above values have to be converted into surface concentration values used to quantify surface decontamination procedures. This is done in Table 1-1.
TABLE 1-1Correlation Between Surface Contamination and Contaminant Dose LevelsSurfacePatient Contamination LevelContaminant DoseContaminationg/patientmg/kg (1)Level, g/m2Worst (2)Nominal (3)Worst (2)Nominal (3)10200.22862.86120.02290.290.10.20.0022.90.0290.010.020.00020.290.00290.0010.0020.000020.030.0003(1) Assumes a Patient Weight of 70 kg (154 lbs)(2) Assumes total skin coverage = 2 m2 of contaminated area(3) Assumes 200 cm2 of contaminated area
Without decontamination, any victim whose whole body was exposed to any CWA agent at the NATO standard load of 10 g/m2 without receiving immediate decontamination would be doomed. Reducing the dose level equal to 10% of the LD50 value, significantly increases survivability; so patients decontaminated to a level of 0.01 gr./m2 would likely survive after having been exposed to any of the agents listed above, except for VX. In the case of VX, the residual surface contamination level should be less than 0.001 gr./m2.
The decontamination of a combatant with an open-wound is a multi-faceted problem that involves both personal decontamination by the wounded individual and casualty decontamination by medical support personnel.
Decontamination after any chemical exposure is most effective when performed within the first minute or two after exposure. This can be performed by the victim or by a squad mate, if one is available. Early action by the patient to decontaminate himself can make the difference between survival (or minimal injury) or death (or severe injury).
Presently, there are no effective personal means of open-wound decontamination. The standard M258A and M291 skin decontamination kits, which would be issued to the combatant, are both specifically contra-indicated for decontamination of open-wounds. The present recommended options for open wound decontamination are irrigation with water, saline, or dilute hypochlorite solution, none of which, other than water, a combatant is likely to possess when wounded.
Walter Reed Army Institute of Research (WRAIR) has demonstrated that a combination of cholinesterase (ChE) pretreatment with an oxime is an effective measure against nerve agents. WRAIR is currently developing sponges in which ChE is covalently linked to a polyurethane matrix. The ChE sponges retained their catalytic activity under conditions of temperature, time and drying where the native soluble enzyme would rapidly denature, and can be reused in conjunction with oximes many times. Such ChE sponges, in the presence of oxime, repeatedly detoxified organophosphates (OP) such as DFP (diisopropyl fluorophosphate) and MEPQ (7-(methylethoxyphosphinyloxy)-1-methylquinolinium iodide). These sponges have the potential of providing a simple wipe method means of detoxifying or decontaminating a wide range of OP-contaminated surfaces. If and when such sponges were included in a skin decontamination kit, they would be expected to provide a means of personal protection that would be safe to use on open-wounds as well as unbroken skin.
While effective against nerve gases, these sponges would have little effect against chemical warfare agents (CWA) that are not OPs, such as mustard (Agent HD). No generally effective method of personal decontamination of an open-wound currently exists.
Decontamination of chemical casualties is an enormous task. The process requires dedication of both large numbers of personnel and large amounts of time. Even with appropriate planning and training, decontamination of casualties demands a significant contribution of resources.
Casualties or other persons entering a medical unit after experiencing a chemical attack are presumed contaminated. In a contaminated environment, casualties ideally enter a medical treatment facility through the contaminated casualty receiving area. The purpose of this area is to provide for the removal of chemical contamination from the casualty before he enters the clean medical treatment facility and as a result maintain a contamination free treatment area. The components of this receiving area are: the arrival point, the triage area, the emergency treatment area, the decontamination area(s), and the “hot line” separating the decontamination and medical treatment areas.
The initial management of a litter casualty contaminated with chemical agents will require removal of mission-oriented gear and its decontamination. This can be done either by physical or chemical removal. Physical removal methods include: wiping with a wet or dry piece of cloth, scraping with a tongue depressor, flushing or flooding the contaminated skin with water or aqueous solutions that can remove or dilute significant amounts of agent, adsorption by granular materials, such as M 291 resin.
Chemical removal methods include soap and water cleansing, oxidation and hydrolysis.
Dilute hypochlorite solution has been commonly used as a means of decontamination that provides both physical and chemical means of removal. Both oxidation and hydrolysis occur in alkaline hypochlorite solution. Within the context of casualty decontamination, it has been standard operating procedure to use 5% hypochlorite solution to decontaminate clothing and equipment and 0.5% hypochlorite solution to decontaminate skin. It was contraindicated for the eye and irrigation of the abdomen, and not recommended for brain and spinal cord injuries. Recent studies with rabbits contaminated with agent GB, indicate that the mortality rate of contaminated rabbits decontaminated with sodium hypochlorite solution is higher than that of control rabbits that were not decontaminated. They also demonstrated that decontaminating with water reduced the mortality rate. Use of dilute hypochlorite solutions for the decontamination of personnel may therefore be contra-indicated.
All military treatment facilities (MTFs) should be prepared to receive mass casualties caused by exposure to chemical agents. A mass casualty situation exists when the number and type of casualties exceed the local medical support capabilities for their care. If the unit follows standard operational procedures (SOPs), an overwhelming backlog of work will rapidly accumulate, since only a limited number of personnel can be assigned to perform decontamination at an MTF. Such backlogs can result in avoidable loss of life and limb with suffering.
To reduce such backlogs, either the number of people or the time required to perform the decontamination will preferably be reduced. While this situation may be improved by the development of improved open-wound decontamination methods, such as the ones discussed in the personal decontamination section above, they may not have significant or sufficient impact on the time required for casualty decontamination. The decontamination protocols now used require large numbers of individual steps both undressing and decontaminating the patient. Decontamination is performed by incremental wiping with wipes from the M 291 and M258A kits, or irrigating with 0.5% hypochlorite from a wash bottle at various levels of disrobing. This is inherently a slow process. If a number of the present steps could be combined, or a more rapid means of agent removal be introduced, it should be possible to reduce the time needed to decontaminate a patient. The logistics of casualty decontamination should be reviewed and alternate methods of patient management and decontamination should be examined.